High blood pressure in pregnancy
High blood pressure in pregnancy can be considered under three main headings:
- Women with high blood pressure who become pregnant
- Hypertension that is brought on by pregnancy
- Pre-eclampsia and eclampsia
Pre-existing high blood pressure
Since many women have high blood pressure and do not know it, it may only be picked up when they have a check up an ante-natal check. Of course many women already know they have it, and are being treated.
If you do have high blood pressure, there are two main considerations. First is to make sure, if you are on treatment, that you are on drugs that are safe for the baby. (Methyldopa or nifedipine are two safe examples). You should definitely not be taking an ACE inhibitor or angiotensin receptor blocker. Your doctor will advise.
If you are not pregnant but are planning to have children, you should also get advice if you are on treatment as it is best not to be on these drugs.
Second, you need to keep a close eye on your blood pressure during the pregnancy to make sure it remains controlled because you are at an increased risk of developing a condition caused pre-eclampsia (see below). Having high blood pressure is not a reason to avoid pregnancy - it should be controlled though.
Pregnancy-induced high blood pressure
For some women, pregnancy can induce high blood pressure. If it develops after 20 weeks of pregnancy, no other abnormalities are detected and it goes away (usually within six weeks of having the baby), it is pregnancy- induced or ‘gestational’ high blood pressure.
In some cases though, the high blood pressure may persist after the pregnancy and it will need to be treated as any other case.
Sometimes, in addition to the raised blood pressure other abnormalities are noted and you may be told you have pre-eclampsia.
Preeclampsia and eclampsia
High blood pressure in pregnancy is can be dangerous for mother and baby. Occasionally, it is the first sign of a condition called pre-eclampsia, which as you might guess can develop further into eclampsia. Usually the rise in pressure develops late in the pregnancy – after 20 weeks. It is diagnosed by testing the urine – if high levels of proteins are detected then you are said to have pre-eclampsia.
The significance of the protein is that the kidneys are not working normally and they therefore allow the protein to escape into the urine. There may be other abnormalities in the blood detected on testing such as slower blood clotting and altered liver function.
This probably sounds scary, but if you have pre-eclampsia, you should not worry. As long as you are well monitored by health professionals and receive supportive care you are unlikely to develop eclampsia or have a problem with your pregnancy. Less than one in a hundred women with pre-eclampsia go on to develop eclampsia.
If pre-eclampsia persists and worsens and the mother develops other complications the condition is called eclampsia. This is rare but serious.
In eclampsia there is very high blood pressure, protein in the urine persists, the brain and liver are affected and so is and blood clotting which is dangerous because of the risk of bleeding during pregnancy. In eclampsia, a common and dangerous feature is the development of convulsions.
During pregnancy, whether or not you have high blood pressure, you should report symptoms such as:
- Severe persistent headaches
- Vomiting which develops later on during the pregnancy (distinct from morning sickness of early pregnancy)
- Stomach pains (usually quite high, below the ribs)
- Sudden and significant increase in swelling of your ankles
- Blurred vision, or other visual disturbances such as flashing lights
With pre-eclampsia, your blood pressure will be controlled with drugs and you may be admitted to hospital for bed-rest. Drugs like magnesium sulphate may be given to you.
The definitive cure for pre eclampsia / eclampsia is to deliver the baby. However it is usually possible to ensure that pre-eclampsia is managed and the pregnancy goes to full term or at least is prolonged so that the baby is not born too premature.
Key points about high blood pressure in pregnancy
- Having high blood pressure is not a reason to avoid pregnancy – you do need to have it under control though
- Untreated high blood pressure in pregnancy is potentially dangerous for the mother and child
- In most cases, high blood pressure in pregnancy does not go on to become pre-eclampsia and the vast majority of cases of pre-eclampsia that are managed carefully do not progress to eclampsia
- If you are pregnant you must have your blood pressure monitored regularly. Testing your urine for protein is also necessary. (you can read more about blood pressure monitoring here).
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